the key is simply an algorithm based on the name used.. if you have it you can just try names til you get one that works. the algorithm is all over the place. But I feel if you have the means to pay you should pay as it's a very small amount and only one time.
you will need a different version of dcx for 6.35. In order to deal with the unicode change in newer versions of mIRC the dcx developers created a new version. So if you are still using 6.35 then you will need the older version. You can get both versions from their website.
just to add to what he posted you are going to sacrifice function for form using a custom nicklist. The default nicklist is always going to perform better in any test. I am a designer so i like things to look a certain way and i am willing to suffer a little less function in return.
you have to learn to accept constructive criticism if you release public works. There are always those that post just to nit pick or troll. Jethro_'s post was an example of the constructive type. Meant only to improve the experience of ppl that wish to use your snippet. No reason to insult him over it. Having dealt with so many casual mirc users over the years I agree with Jethro_. Most will simply copy and paste thus bypassing the on load.
I made one with dcx.dll but really it's a waste of time and effort. It's buggy if javascript of the page isn't perfect and many times you just end up freezing the window. You are better off just using /url in mIRC. I created one for a semi-public script and it was always more of a problem than a solution.